This project deals with the issue of restoring lower limb function in patients with severe arthritis of the ankle or hindfoot who require the use of a standard ankle foot orthosis (AFO) or hindfoot orthosis (articulated, non- articulated) and to lock the ankle or hindfoot for stability during gait. These patients have stiff, arthritic joints which are painful and impair their ability to walk. Currently, these types of patients are fitted with a conventional rigid polypropylene AFO to limit movement. These devices restrict ankle, hindfoot, and midfoot movement during walking. This may produce inefficient gait, unnecessarily immobilize unaffected joints, and may not be tolerated by debilitated patients because of their weight or bilateral impairments. The goal of this project is to test two lightweight hindfoot orthoses (articulated and non-articulated) and a standard AFO in normal and arthritic subjects in three different walking environments. In level, side-slope, and ramp walking, they propose to: 1) perform objective measurements of gait patterns for the three orthoses in normal subjects; and 2) test the performance of these three orthoses in patients with ankle or subtalar arthritis. The results of these studies are expected to improve the efficacy of gait in patients with arthritis who require conventional AFO treatment. In addition to patients with arthritis, these orthoses will be useful for patients with ankle instability, subtalar instability, and neuromuscular disorders.